AT&T Email to Office 365 Migration

This guide explains how to migrate AT&T (ATT) email to Office 365 (Microsoft 365) through IMAP. It applies to supported AT&T Mail domains such as @att.net and related legacy domains, with the migration focused on email messages, attachments, folders, and supported message metadata.

However, migrating from AT&T email to Office 365 can be challenging, particularly for users unfamiliar with the technical aspects. Native migration methods often require manual configurations and carry risks such as data loss, interrupted service, or incomplete transfers. These approaches can also be time-consuming and prone to errors, especially in large-scale or multi-user environments.

The EdbMails IMAP Migration Tool provides a guided AT&T-to-Microsoft 365 email migration workflow for supported messages, attachments, folders, and common message properties. It supports single and bulk projects, mapping, filters, follow-up passes, and migration reports.

For destination-wide Microsoft 365 prerequisites, authentication, mapping, and cutover planning, use the main IMAP to Office 365 migration guide.

Where supported and selected, EdbMails can assist with target mailbox creation and mailbox mapping. Verify Microsoft 365 licensing and review every source-to-target mapping before migration. Customized target-folder selection and the script-free workflow can reduce repetitive administration.

1. Why do users Migrate emails from ATT to Microsoft 365?

   1. Microsoft 365 allows users to integrate AT&T email into Outlook 365 for unified email management, reducing the need to switch between platforms.
   2. Outlook 365 offers advanced features such as intelligent sorting, categorization, and powerful search capabilities, improving email organization and retrieval.
   3. Users can access emails, calendar events, and contacts offline, ensuring productivity even without an internet connection.
   4. Seamless integration with other Microsoft services like OneDrive, Teams, and SharePoint creates a centralized workspace for communication and collaboration.
   5. Microsoft 365 offers scalable storage, allowing users to adjust storage space according to their needs.

   For these reasons, many users choose to migrate from AT&T email to Office 365 using EdbMails.

2. Common Migration Challenges & Solutions

   1. Authentication Errors

   Challenge: Users may face login or authentication failures, especially if basic authentication is disabled.

   Solution: For the AT&T source connection, use the authentication method supported by AT&T Mail. AT&T provides IMAP access through imap.mail.att.net on port 993 with SSL and recommends a Secure Mail Key for clients that do not use OAuth. The Microsoft 365 target connection uses supported Microsoft authentication.

   2. Slow Transfer Speed

   Challenge: Large mailboxes or limited bandwidth can cause slow migration speeds.

   Solution: EdbMails supports concurrent processing and includes Microsoft 365 throttling-handling logic. Additionally, its delta migration feature transfers only new or updated emails, improving performance and minimizing repeated data transfer.

   3. Folder Mismatch Issues

   Challenge: Source and destination folders may not align properly, leading to misplaced emails or incomplete folder mapping.

   Solution: EdbMails includes automatic mailbox and folder mapping, for aligning system folders (like Inbox, Sent, Drafts).

3. ATT email to Office 365 Migration Plan

   Planning is one of the most important steps before you begin the ATT email to Office 365 migration. Here is a checklist of points to consider before you migrate.

   • Determine the size of the data and the number of mailboxes you want to migrate.
   • Make a list of all the data and permissions from the ATT email that you want to transfer.
   • Create appropriate user mailboxes on Office 365 and assign licenses to them.
   • Ensure you have enough network capacity and bandwidth to migrate.
   • Communicate the migration plan and flow to your end users.

4. ATT email to Microsoft 365: Pre-migration Activities

   1. Find the IMAP server name of your ATT email server. You can find this information from your server’s dashboard settings or by connecting your email system to Outlook.
   2. Have the users email address, passwords, IMAP hostname and port number.
   3. Create mailboxes on your target Office 365 server. You can choose the option to automatically create target mailboxes in EdbMails. If you prefer to create them manually, refer to the links below.
      1. Add users and assign licenses to Office 365 user
      2. Assign Microsoft 365 licenses to user accounts
   4. If you have a custom email domain from your hosting provider to which you want to migrate and receive emails, you must add and verify the domain on Office 365.

        Steps to add a custom domain to Office 365 and Steps to add DNS records to connect your domain.

   5. Configure Office 365 to send and receive large messages.

        Follow the steps to increase the message size on Office 365 to 150MB and see tips to optimize IMAP migration to Exchange online.

5. Steps to Migrate emails from ATT to Office 365

   • Step 1: Download and install EdbMails IMAP migration software

     • Download and install EdbMails IMAP migration software

       

     • Start the EdbMails application on your computer.
     • Enter your registered email ID and password, then click ‘Login’. If you are accessing EdbMails for the first time, choose ‘Start Your Free Trial’ to continue with the trial version.

        Note: The trial version includes all essential features and permits migrating up to 30 items per folder. To migrate all eligible items for licensed mailboxes, purchase the required IMAP Migration license from the official EdbMails website.

        Click here to know IMAP Migration Pricing Details.

       Once the purchase is completed, close the software and reopen it. Log in again with the same email ID and password used during the purchase to activate your license successfully.

       

     • Choose the ‘IMAP (Gmail, Outlook and more) Migration’ option to begin the transfer process.

       

     • Select ‘IMAP to Office 365 Migration’.

       

     • You can continue with the default job name or select ‘New Job’ to create and assign a customized name based on your preference.

       

   • Step 2: Connect to the source ATT email server

     • To connect a single AT&T email account for migration, click ‘Single User / Account Migration’, choose the suitable connection option such as ‘Connect to IMAP Server’ or ‘Connect to POP3 Server’. Click ‘Next’ to proceed.

       

     • Choose the AT&T IMAP host name imap.mail.att.net and port 993 with SSL. Enter the complete AT&T email address and the password or Secure Mail Key required for the source connection.
     • Once the credentials are entered, click the ‘Login’ button. EdbMails will establish a secure connection with the ATT server mailbox and retrieve the mailbox data required for migration.

       

     • To migrate multiple ATT server mailboxes at once, select ‘Multiple (bulk) Users/Accounts Migration’, choose the suitable connection method such as ‘Connect to IMAP Server’ or ‘Connect to POP3 Server’.
     • Then proceed by clicking ‘Next’.

       

     • Click ‘IMAP Migration CSV File’ and choose a destination folder on your local computer to save the CSV file.

       

     • Open the CSV file and enter the required details such as each user’s email address, password, IMAP server hostname, and port number. Once all information is added, save your changes and close the CSV file.

       

     • Now, click the 'Load Modified CSV File' button, open the CSV file and click ‘Next’ to proceed.

       

   • Step 3: Select the mailboxes or folders to migrate

     • Select the mailboxes or specific email folders you want to migrate from your AT&T server account. You can choose all mail items or filter by folders such as Inbox, Sent Items, or Custom Folders based on your requirements. Once selected, click ‘Next’ to proceed with the migration process.

       

   • Step 4: Connect to target Office 365 server

     • Click the ‘Add New Connection’ button to set up a new connection to your target Office 365 account. If you want to use an existing connection, simply select it from the list and click ‘Connect to Existing’

       

     • Select the appropriate connection settings based on your migration requirements, then click ‘Next’ to proceed to the next step.

       

     • Choose your preferred secure authentication method for the target Office 365 and click the ‘Login’ button.

       

     • Authenticate by signing in through the official Microsoft login page using your Office 365 credentials.

       

     • After successful authentication, choose any one of the following options to load the mailboxes:

       i) Load Mailboxes Automatically: EdbMails loads and displays the mailboxes automatically once you sign in, simplifying the configuration process. If the automatic mailbox list does not return every required target, use the CSV-loading option below and verify the destination mailbox list before continuing.

       ii) Load Mailboxes using CSV file: If the automatic method does not retrieve all mailbox names, select the ‘Load Mailboxes using .CSV file’ option to manually import and load the required mailboxes.

       iii) Load Mailboxes from previous list: Quickly access the mailboxes from the previously saved list imported during your last session.

     • Choose ‘Load Mailboxes Automatically’ and click ‘Next’ to continue.

       

   • Step 5: AT&T email to Office 365 mailboxes mapping

     • Select a preferred option to map the source mailboxes and folders with their corresponding mailboxes and folders on the target Office 365 account.

       

     • EdbMails lets you automatically create the required mailboxes in your target Office 365 account.
     • It also automatically maps your source AT&T mailboxes and folders to the matching ones in Office 365, making large migrations easier to manage.

       

   • Step 6: Start the AT&T to Office 365 migration

     • Review and confirm the mailbox mapping to ensure accuracy. Once verified, click the ‘Start Migration’ button to initiate the transfer to Office 365.

       

     • Click the ‘View Logs’ button to access the full migration report. The report provides detailed information, including the mailbox mapping, an overall summary of the migration, and the item count for each mailbox and folder that was migrated.

       

6. ATT email to Microsoft 365 Post-migration Tasks

   • Step 1: Update the MX records to point to Office 365

     If you have not done this step previously, Change the MX records to enable and receive email messages on the target Office 365 server. In addition, configure the Autodiscover record to allow Outlook to connect to the migrated mailboxes.

   • Step 2: Create a new Outlook profile for users in the new domain

     Configure and recreate the Outlook profile for each user in your domain if Outlook has problems connecting to Office 365 mailboxes.

7. Troubleshooting Guide for ATT email to Office 365 Migration

     For troubleshooting, check out our knowledge base articles. If you have additional questions, browse the FAQs or contact our dedicated support team for personalized assistance.

Frequently Asked Questions

1. How long does an AT&T to Office 365 migration take?

   The migration duration depends on factors such as mailbox size, number of users, internet speed, and server response time. Using EdbMails, small migrations can complete within a short time, while large-scale or organization-wide migrations may take longer. The tool supports delta migration, allowing users to continue from where they left off without restarting.

2. Does EdbMails migrate attachments and contacts?

   EdbMails migrates supported IMAP email data, including email messages, attachments, folders, and message metadata. Contacts and calendars are not transferred through standard IMAP migration because IMAP is an email protocol and does not carry those item types.

 Learn more about EdbMails IMAP migration Tool.

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